This application claims the benefit of Japanese Application No. 10-71713 which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a device for rockably supporting a steering column for a tilt-type steering apparatus. The device for rockably supporting a steering column for a tilt-type steering apparatus is adapted to support the front part of the steering column to allow rock thereof to freely adjust the height of a steering wheel. The present invention further relates to a device for rockably supporting a steering column for a tilt-type steering apparatus that allows the steering column to be displaced forward while absorbing energy generated upon a secondary collision (collision of a driver with a steering wheel).
2. Related Background Art
To adjust the height of the steering wheel of a car to meet the physical constitution or a driving posture of the driver, a height adjustment apparatus of a steering wheel called a tilt-type steering apparatus is conventionally widely used. A support device for rockably supporting the front part of the steering column to allow rocking movement and adjust tilt of the steering column is incorporated in such tilt-type steering apparatus.
FIGS. 9 to 11 show an example of the tilt-type steering apparatus incorporating such support device of the steering column disclosed in Japanese Utility Model Application Laid-Open No. 4-114872. In these figures, a fixed or stationary bracket 1 is supported and fixed to the car body at the lower face of the dashboard. This fixed bracket 1 has a pair of vertical walls 2 that are in parallel to each other, and a pair of elongated holes 3 that are respectively formed in a vertical direction (up-and-down direction in FIG. 9) at positions of the paired vertical walls 2 to be aligned with each other.
An up and down movable bracket 5 is fixed to an intermediate portion of a steering column 4 through which a steering shaft 10 is inserted, and this movable bracket 5 is sandwiched between the paired vertical walls 2. Both ends of a movable rod 6 that passes through the movable bracket 5 in the lateral direction (direction perpendicular to the sheet in FIG. 9) are projected from the outer sides of the paired vertical walls 2 through the paired elongated holes 3. A tilt lever 7 is supported at one of these ends. This tilt lever 7 is operable to engage the fixed bracket 1 with the movable bracket 5 or release such engagement.
When the tilt lever 7 is in the state shown in FIG. 9, the inner sides of the vertical walls 2 of the fixed bracket 1 are urged upon the outer side of the movable bracket 5 by a nut (not shown) that is fixed to the center of rotation of this tilt lever 7 and threadably engaged with the end of the movable rod 6. Thus, the movable bracket 5 is fixed to the fixed bracket 1. At the same time, an edge of a stopper 8 formed at the base end of the tilt lever 7 and a stretching wall 9 formed on the fixed bracket 1 are brought into abutment.
When the tilt lever 7 is rotationally moved from the state shown in FIG. 9 in the clockwise direction in the same figure, the edge of the stopper 8 and the stretching wall 9 are separated from each other and the urged state mentioned above is released. Then, the movable bracket 5 is freely movable upward or downward.
A support bracket 11 is provided on the outer periphery of the front-end portion of the steering column 4 (the left end part in FIG. 9). This support bracket 11 is integrally formed of a metallic plate having elasticity such as a steel platemade by press-forming. An upper edge portion of this support bracket 11 constitutes a mounting portion 12 that is bent at a right angle backward (to the right in FIGS. 9 and 10) to be attached to the car body. Circular holes 13, 13 each for-receiving a mounting bolt are formed at both ends of this mounting portion 12. A circular hole 15 for receiving the steering column 4 is formed at the center of a support portion that is extended downward from the front edge of the mounting portion 12 at a right angle. Plural support flaps 19 (four in the illustrated example) are formed at intervals on the periphery of the circular hole 15 with cut-away portions 17 each formed between the edges of adjacent support flaps 19 in the circumferential direction. Arched walls 16 are formed on the inner edges of these support flaps 19 to be bent at a right angle backward from the inner edges of the support flaps 19. These arched walls 16 jointly constitute a cylindrical support portion 18. The arched walls 16 are formed such that the inner diameter of the cylindrical support portion 18 in a free state is slightly smaller than the outer diameter of the front part of the steering column 4.
Into the cylindrical support portion 18 of the support bracket 11 constituted as described above, the front-end portion of the steering column 4 is inserted, elastically deforming outward in the radial direction the arched walls 16 constituting this cylindrical support portion 18. Then, after the insertion, the front-end portion of the steering column 4 is elastically supported on the inner side of this cylindrical support portion 18. In this state, the front-end portion of the steering column 4 is elastically urged over the entire circumference thereof (except the cut-away portions 17 mentioned above) by the cylindrical support portion 18 constituted by the arched walls 16. Further, the support bracket 11 is fixed to the car body by bolts that pass through the respective circular holes 13, 13 of the mounting portion 12 from below.
In the case of a tilt-type steering apparatus constituted as described above, when the steering column 4 is rocked upon the height adjustment of the steering wheel, the arched walls 16 constituting the cylindrical support portion 18 are elastically deformed. At the same time, when an inner peripheral surface of a part of the arched wall 16 slides on the outer peripheral surface of the steering column 4, smooth rocking of the steering column 4 is allowed. In the state in which the front-end portion of the steering column 4 is thrust into the cylindrical support portion 18, this cylindrical support portion 18 elastically suppresses the front-end portion of the steering column 4 substantially over the entire periphery thereof.
The conventional tilt-type steering apparatus constituted as described above has significant drawbacks. For example, in the conventional structure, it is impossible for the support bracket 11 to stabilize a collapse load required for displacing the steering column 4 forward in a secondary collision, as described above. More specifically, in the case of the conventional structure, the arched walls 16 are formed as being bent at right angles backward from the inner peripheries of the support flaps 19. As a result, when the front-end portion of the steering column 4 is displaced forward in the secondary collision, the leading edge of all or a part of the arched walls 16 (the right edge in FIGS. 9 and 10) possibly bites into the outer peripheral surface of the steering column 4. In this case, it is difficult for the steering column 4 to be displaced forward and the collapse load possibly becomes unstable. For this reason, in the conventional structure, the steering column 4 is formed by telescopically combining an outer column and an inner column to be contracted in the secondary collision. However, such contractible steering column costs more, compared with a single-column structure steering column.
When the front-end portion of the steering column 4 is inserted into the cylindrical support portion 18 from the rear side (the right side in FIGS. 9 and 10) of the support bracket 11 so that the front part of the steering column 4 is inserted into the cylindrical support portion 18, the front edge of the steering column 4 and the leading edges of the arched walls 16 tend to mutually interfere. Consequently, it becomes troublesome to mount the support bracket 11 on the front part of the steering column 4. On the other hand, when the steering column 4 is inserted into the cylindrical support portion 18 from the front side (the left side in FIGS. 9 and 10) of the support bracket 11, it is necessary to move the support bracket 11 inserted from the rear end side of the steering column 4 to the front part of the steering column 4 while elastically deforming the arched walls 16, 16 outward in the radial direction thereof. In addition, in this case, it becomes troublesome to mount the support bracket 11 on the front part of the steering column 4.
The support bracket 11 is mounted on the front-end portion of the steering column 4 by the elasticity of the cylindrical support portion 18. For this reason, when the support bracket 11 mounted on the front part of the steering column 4 is to be conveyed or assembled in the car body, if this support bracket 11 strikes another part of the car or the like, the support bracket 11 possibly deviates from the normal mount position in the front part of the steering column 4. When the mount position of the support bracket 11 is out of place, bolts inserted through the circular holes 13, 13 (see FIG. 11) of the mounting portion 12 cannot be threadably engaged with screw holes formed in a part of the car body. Consequently, it is necessary to mount the mounting portion 12 with care so that the mount position of the support bracket 11 is not out of place. Thus, the assembling workability thereof decreases correspondingly.
There is also a demand for giving an energy absorbing function to the support bracket for supporting the front part of the steering column to allow rocking movement by its own elasticity as described above.
A first object of the present invention is to provide a device for rockably supporting a steering column for a tilt-type steering apparatus that is free from the above-mentioned drawbacks of the conventional technology.
A device for rockably supporting a steering column for a tilt-type steering apparatus according to the present invention comprises a support bracket formed integrally of a plate member having elasticity for rockably supporting the front part of a steering column of the tilt-type steering apparatus to the car body, a mounting portion for mounting the support bracket on the car body, and a support portion for supporting the steering column on the support bracket.
The support portion comprises a circular hole for passing the steering column and a plurality of support flaps formed between each adjacent two of a plurality of cut-away portions formed at intervals outward in the radial direction on the inner periphery of the circular hole.
Specifically, the device for rockably supporting a steering column for a tilt-type steering apparatus according to the present invention for achieving the above object is provided with a plurality of arched walls for constituting a cylindrical support portion which elastically presses the outer periphery of the front part of the steering column substantially over the entire periphery thereof on the inner periphery of each of the plural support flaps. Each of these arched walls is provided as bending forward from the inner periphery of each of the support flaps. Then, the front part of the steering column is supported to be rockable on the inner side of the cylindrical support portion by thrusting the front part of the steering column into the cylindrical support portion while elastically deforming each of the arched walls outward in the radial direction of the cylindrical support portion.
A second object of the present invention is to provide a device for rockably supporting a steering column for a tilt-type steering apparatus to satisfy the above-mentioned demand. In a device for rockably supporting the steering column for achieving the second object, substantially the entire outer peripheral surface of the front part of the steering column is elastically pressed by the inner periphery of each of the support flaps, and in the central portion of the inner periphery of one of the support flaps provided either at the upper end or the lower end of the circular hole there is provided a protruding portion protruding more inward in the radial direction, than other parts of the inner periphery. Then, the front part of the steering column is thrust into each of these support flaps while the support flaps are elastically deformed outward in the radial direction of the circular hole. At the same time, the protruding portion and a slit, which is formed at a position aligned with the protruding portion in the front part of the steering column for freely passing the protruding portion, are engaged with each other, thereby supporting the front part of the steering column inside the support flaps to be rockable about the engagement portion between the protruding portion and the slit as the center of rock. Further, when the steering column is displaced forward in the axial direction at collision, an abutment means which is a part of the outer periphery of the steering column and provided in the rear of the support bracket and a part of the support bracket are brought into abutment, thereby absorbing the energy generated upon the collision while elastically deforming the support bracket.
In the case of a device for rockably supporting a steering column for a tilt-type steering apparatus of the present invention constituted as described above, when the steering column is rocked upon the height position adjustment of the steering wheel, the support flaps and the arched walls for constituting the support portion are elastically deformed, thereby allowing the steering column to be rocked.
In the device for rockably supporting a steering column for a tilt-type steering apparatus for achieving the first object mentioned above, the arched walls that constitute a cylindrical support portion for elastically supporting the outer peripheral surface of the front part of the steering column are provided as being bent at right angles forward from the inner periphery of each of the support flaps. For this reason, when the steering column is forward displaced in a secondary collision, the leading edge of each of the arched walls does not bite into the outer peripheral surface of the steering column. Consequently, even if this steering column is not contractible, a collapse load in a secondary collision can be stabilized without fail. In addition, when the front-end portion of the steering column is inserted into the cylindrical support portion from the rear side of the support bracket, the arched walls do not interfere with the insertion. Consequently, a work for inserting the leading end of the steering column into the cylindrical support portion can be performed easily.
In the device for rockably supporting a steering column for a tilt-type steering apparatus for achieving the second object mentioned above, the inner periphery of each of the support flaps is formed in an edge-like shape. Consequently, in the state that the outer peripheral surface of the front part of the steering column is elastically urged upon the inner periphery of each of the support flaps, it is possible to have a large contact pressure between the outer peripheral surface and the inner periphery. It is also possible to have a larger rigidity for supporting the front part of the steering column by the support bracket. Note that the inner periphery of each of the support flaps is brought into contact as being substantially perpendicular to the outer peripheral surface of the steering column or in a slightly forward inclined manner. For this reason, even when the steering column is forward displaced in a secondary collision, the inner periphery of each of the support flaps is immediately displaced in a direction in which it is retracted from the outer peripheral surface of the steering column. Accordingly, the inner periphery of each of the support flaps does not bite into the outer peripheral surface of the steering column to inhibit the forward displacement of the steering column. When the support bracket is assembled in the front part of the steering column, a protruding portion that is formed on the inner periphery of the support flap provided either at the upper end or at the lower end of the circular hole and a slit that is a part of the outer peripheral surface of the front part of the steering column and is formed in a part aligned with the protruding portion are brought into engagement. Accordingly, when the mounting portion of the support bracket mounted on the front part of the steering column is to be assembled in the car body, even if this support bracket strikes another car part or the like, the support bracket does not deviate from the normal mount position in the front part of the steering column on the basis of the existence of the engagement portion between the protruding portion and the slit. Since the steering column is rocked around the engagement portion between the protruding portion and the slit, a range of movement of the front part of this steering column can be controlled securely. Accordingly, it is possible to prevent the front part of the steering column from interfering with a peripheral member at the time of height adjustment of the steering wheel.
When the steering column is displaced forward in a secondary collision, an abutment means that is a part of the outer peripheral surface of the steering column and is provided in the rear of the support bracket and a part of this support bracket are brought into abutment, thereby sufficiently absorbing the energy generated upon the secondary collision while plastically deforming the support bracket. For this reason, it is possible to provide the support member with the energy absorbing function.